This description relates to specifying and applying rules to data.
In some examples, one or more rules may be applied to records in a data processing system. For example, rules may be used to verify the quality of the records or to trigger events based on information included in the records. The rules may be specified by a developer using a user interface. In some examples, the results of applying rules may differ, depending on whether the rules were applied during a development phase or a production phase.